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E39 (1997 - 2003) The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

Please help. Problem ...plenty of heat coming out of the drivers side. Most time heat coming out of the passenger side. Then the passenger side cycles cold then hot then cold. Blowers are working properly. It works for days properly then when it is really cold outside it "may" have an intermittant problem. somes days it is fine. Is it the heater valve? If so does any one have pictures of where it is located for DIY job? It is 9 degrees and if I need my defroster I will be in trouble. Thank you for any replies.

The heater valve is on the tire well drivers side under hood, can see on realoem.com. I'm wondering if it's not that and instead need to bleed air out of the system? Have you had any overheating problems? How's you coolant level?

My car had intermittent heater problem 3 months ago. After a few times, it started to overheat (but no heat for cabin) and stayed that way. I started the cooling DIY but couldn't remove the clutch nut. After refilling coolant to drive the car to the shop for removing the clutch nut, the cooling (heating) system and cabin heating became normal. While having the above problems, the engine-to-radiator hose was hot and had high pressure while the opposite hose was almost empty and cold - coolant did not flow through the radiator. Refilling coolant made it work again so thermostat was probably OK. I ended up replacing it.

Try some simple fixes such as refill/re-bleed coolant, test the thermostat using cold or hot water (if you had to take it out).

Also, a small thing you can check is when the engine and coolant are hot, carefully use your hand to check the pressure (by squeezing) and temp on the two main radiator hoses.

It appears that the automatic "may" be dual zoned, hence the 3 pipes. One feed/return one for driver, one for pass. This is a big fat guess and I could be 100% wrong here. My guess is that you have the automatic version with the 3 pipes that go to the water valve. As a quick check when you are having this issue check the 3 hoses. Does one change in temperature when this issue is happening? If so, then you know know what is causing it. Now is it the water valve, or the control to the water valve??

Just dug this up from the WDS wiring link shown in my sig.
Temperature control

Nominal temperature value setting

The temperature is selected separately for the driver's and passenger's side by the plus/minus buttons. The nominal values are shown in the LC display in steps of 0.5 o C or 1 o F. The displayed values correspond to a comfort temperature which can deviate from the air outlet temperatures.

The temperature control function is deactivated when the temperature on the driver's side is set to minimum or maximum. Both water valves are closed in the minimum position and opened in the maximum position.

Thank you for all your replies. Had the coolant replaced and when they did they found a small leak AND when they took off the the heater hose(main neck) connected to the radiator the plastic neck fell apart. They reattached the hose although the plastic neck is shorter. Have heat on both sides of the cabin now. Do I have to get a whole new radiator?

so you fixed the problem by draining and refilling your coolant? I have the same problem. I was told it can be the valve/pump control. Others say water pump while some say coolant levels. I'd hate to go dropping money on parts that don't need to be replaced.

Thank you for all your replies. Had the coolant replaced and when they did they found a small leak AND when they took off the the heater hose(main neck) connected to the radiator the plastic neck fell apart. They reattached the hose although the plastic neck is shorter. Have heat on both sides of the cabin now. Do I have to get a whole new radiator?

Whoever the mechanic working on your car does not know BMW.
You need a cooling system overhaul.

Yes, replacing the coolant level did work and still is working. I would try that first. I think a good test would be to put the car on a hill ( don't remember if it is front up facing the hill or front down(down the hill). Anyway, when I did that before I had my coolant replaced the heat would work on the side that didn't work. Hope that helps.

Hmm...I knew it was not the thermostat since I have replaced it 3 times and know what to look for. I had already replaced the WP after it disintergrated a few years back. I may at some point have to replace the radiator because of the cuff breaking off and making a shorter connection. But everything is working just fine. If it aint broke don't fix it.

okay so I did a full cooling system overhaul (thanks to the fest for the parts list and cn90 to help me locate the best prices online for everything). I am now experiencing in the frigid temps of the Midwest that my heater is no longer blowing cold air. Started on the passenger side, now both sides. After a period of time it was warming up but now it doesn't even seem to warm up. I have had the message for low coolant levels for sometime now and just haven't addressed it. going to my indy Monday to have them change the oil so do I need to also have them bleed the system to get any air out? The temp gauge actually hopped up to the red for a second and then back to middle so I am not sure exactly what to do? heater valve replacement? again, I overhauled the entire cooling system less than 2 years ago (all parts).

Thank you and lastly there is an engine ticking noise at idle when its as cold as its been. that may be another project in itself? I am scheduled for a maintenance check up at the indy too so hopefully he finds any and all issues that we can take care.

I went ahead and put some more coolant into the reservoir as it was actually low a little bit then drove to work w/o bleeding yet. Warm air started coming out shortly thereafter so I think the problem with the heated air may be solved. haven't bled the system yet but may still do that later as needed and have the coolant in the trunk if ever in a serious jam. Possible slow leak somewhere in the cooling system it seems even though I redid the entire system only 2 years ago. check coolant level indicator still coming up and has for awhile. what's triggering that? would a bleed help resolve that?

update... bled the system and check coolant level warning gone with plenty of warm air coming out in the dreaded cold. nice to see a cluster free of warnings. damn weather just needs to get warm up ...

I'll revive this old thread with a riddle. My E39 wagon is blowing cold air when the air is coming out of the main vents. When the defroster button is pushed, the heater fan goes to full speed and hot air comes out of the windshield vents. Also, I have a battery draining issue that seems to point towards the FSU. It is winter in Canada and I'm not using the wagon, so even though I have a replacement FSU, I have not installed it, waiting for the spring to do so. Does this sound familiar to anyone?